1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head that discharges liquid and, in particular, a method for manufacturing an ink jet recording head that records an image by discharging ink to a recording medium.
2. Description of the Related Art
A liquid discharge head that discharges liquid is used, for example, as an ink jet recording head in an ink jet recording system.
An ink jet recording head typically includes a flow path, an energy generating element which is provided at a part of the flow path to generate energy for discharging ink, and a fine ink discharge port (referred to as an “orifice”) for discharging ink.
As a method for manufacturing the ink jet recording head, U.S. Pat. No. 4,657,631 discusses the method that includes forming a pattern of flow paths with a photosensitive material on a substrate on which energy generating elements are formed, and coating the substrate with a covering resin to form a layer which is a path forming member to cover the pattern. The method further includes forming discharge ports on the covering resin layer and removing the photosensitive material used as the pattern. According to the manufacturing method, application of a photolithographic approach that is used in the semiconductor field enables highly precise and fine fabrication of the flow path and the discharge ports. In recent years, further improvements in recording speed and recording quality are required and therefore a number of discharge ports of an ink jet head increases and a dimension of each discharge port becomes very small, specifically a diameter of the discharge port is approximately several tens of μm to several μm.
To form discharge ports with higher precision, the inventors attempted to form the discharge ports with light of i-line single wavelength as an exposure light source in the method discussed in U.S. Pat. No. 4,657,631. Although the inventors intended to make circular discharge ports, the formed discharge ports had irregular shapes and some of them adversely affected discharge of liquid.
The inventors investigated the result of the experiment and found following possible causes for the irregular shapes described above. More specifically, the light used for exposure reaches the substrate, reflects on the substrate surface, and after that reaches the resin for forming a discharge port, so that the shapes of the discharge ports are made different from a desired one.